In the March 2007 issue of BioScience, an international team of 19 researchers calls for better forecasting of the effects of global warming on extinction rates. The researchers, led by Daniel B. Botkin, note that although current mathematical models indicate that many species could be at risk from global warming, surprisingly few species became extinct during the past 2.5 million years, a period encompassing several ice ages. They suggest that this "Quaternary conundrum" arises because the models fail to take adequate account of the mechanisms by which species persist in adverse conditions. Consequently, the researchers "believe that current projections of extinction rates are overestimates." A critical review of the four types of model now in common use leads the team to identify various simplifying assumptions in the models that can lead to biases.
The authors make eight recommendations for improving forecasts of extinction rates under global warming. The recommendations cover a wide range, from clarifying the definition of biodiversity to improving existing models and developing better ones. They include, for example, the suggestion that current models need to be more rigorously tested, that explanations of extinction other than climate change need to be more thoroughly considered, and that better data should be brought to bear on the problem, especially information from the fossil record of Quaternary ice ages. The authors acknowledge, however, that they do not fully understand why so many species persisted during these ice ages, and caution that some genetic research suggests that species might in fact be more vulnerable than the fossil record indicates.